1. Field of the Invention
This invention relates to a composite nonwoven fabric which is particularly suited for use as an apparel insulating interliner. More particularly, the invention concerns such a fabric which includes a batt of staple polyester fibers that is attached to a nonwoven sheet of continuous polyester filaments.
2. Description of the Prior Art
Many nonwoven materials have been suggested and used for insulating interliners. J. L. Cooper and M. J. Frankosky, "Thermal Performance of Sleeping Bags," Journal of Coated Fabrics, Volume 10, pages 108-114 (October 1980) compares the insulating value of various types of fibrous materials that have been used as interliners in sleeping bags and other articles. Among the products compared are polyester fiberfill of solid or hollow or other special fibers and a product of 3M Company (St. Paul, Minn.) called "Thinsulate." Generally, polyester fiberfill is made from crimped polyester staple fiber and is used in the form of quilted batts. Usually, batt bulk and bulk durability are maximized in order to increase the amount of thermal insulation. Hollow polyester fibers have found widespread use in such fiberfill batts because of the increased bulk they offer, as compared to solid fibers. In certain fiberfill materials such as Hollowfil.RTM.II, a product of E. I. du Pont de Nemours and Company (Wilmington, Del.), the polyester fibers are coated with a wash-resistant silicone slickener to provide additional bulk stability and fluffability. For fiber processability and in-use bulk, slickened and non-slickened fiberfill fibers for use in garments have usually been in the range of 5 to 6 denier (5.6 to 6.7 dtex). A special fiberfill, made from a blend of slickened and non-slickened 1.5-denier polyester staple fibers and crimped polyester staple fiber having a melting point below that of the other polyester fibers, in the form of a needle-punched, heat-bonded batt, is reported to exhibit excellent thermal insulation and tactile aesthetic properties. Such fiberfill batts are also discussed in U.S. Pat. No. 4,304,817. "Thinsulate" is an insulating material in the form of a thin, relatively dense, batt of polyolefin microfibers, or of the microfibers in mixture with high denier polyester fibers. The high denier polyester fibers are present in the "Thinsulate" batts to increase the low bulk and bulk recovery provided to the batt by the microfibers alone. For use in winter sports outerwear garments, these various insulating materials are often combined with a layer of film of porous poly(tetrafluoroethylene) polymer of the type disclosed in U.S. Pat. No. 4,187,390.
Although the above-described prior-art nonwoven materials have been useful as insulating interliners, various improvements would significantly enhance their utility. For example, needle-punched and/or bonded batts often are excessively stiff, lack conformability and sometimes require more weight than is desired for the needed insulating value. Batts containing polypropylene fibers generally cannot be dry-cleaned and, because of their low melting temperature, are difficult to laminate and often suffer damage in home-laundry dryers. Bulky batts, which are neither bonded nor needle-punched, generally lack strength, dimensional stability and resilience and are difficult to handle in cutting, lamination and other fabrication operations. Among the important characteristics desired in a material intended for use as an insulating interliner are a high insulation value per unit weight, lack of stiffness, good strength, ability to be dry-cleaned and sufficient resilience to avoid excessive crushing during lamination and use.
Though not related specifically to apparel insulating interliners, a wide variety of spunlaced nonwoven fabrics are known in the art. For example, British Pat. No. 1,063,252 and U.S. Pat. Nos. 3,493,462, 3,508,308 and 3,560,326 disclose stable, nonapertured, jet-tracked, spunlaced nonwoven fabrics of hydraulically entangled polyester fibers and filaments. Usually, the spunlaced fabrics are produced by subjecting a fibrous batt to closely spaced, high energy flux, columnar jets of water. In commercial operations, the jets are usually arranged in rows in which the number of jets per centimeter is in the range of 10 to 25. The use of widely spaced jets also has been disclosed. For example, in British Pat. No. 1,063,252, Example I describes the hydraulic stitching of a batt of polyester fibers in "quilt-like" fashion to form "seams" that are spaced 3/4-inch (1.9-cm) apart in the batt and Example II describes the steaming of the stitched batt. However, neither example records detailed characteristics of the stitched batt. Applicant has found that such stitched batts are generally very weak and difficult to handle.
It is also known, though again not with respect to nonwoven fabrics for apparel insulating interliners, that various fibrous layers, such as batts, webs, scrims, sheets and papers, can be combined by means of hydraulic entanglement techniques into spunlaced nonwoven fabrics. For example, Canadian Pat. No. 841,938 discloses "laminating," by means of hydraulic entanglement, batts of staple rayon fibers, or sheets of paper (i.e., wood pulp fibers) to sheets of continuous polyester filaments. At least 10 jets per inch (4 per cm) and preferably 30 to 50 per inch (12 to 20 cm) are suggested for forming the spunlaced "laminates."
Although the known spunlaced nonwoven fabrics have found wide application in many end uses, none of the spunlaced fabrics were used for apparel insulating interliners, nor would the spunlaced fabrics have adequately satisfied the technical requirements for such interliners.
It is an object of the present invention to avoid or at least significantly reduce, the shortcomings of the above-described insulating materials and to provide a new composite nonwoven fabric that is particularly suited for use as an apparel insulating interliner.